My best multiboot plugin is NFR4XBoot
simple , fast and stable.
You can install 10 images
But if you do my trick you will install more than that without modifying anything.
First send the attached to their folders by DCC and restart.
Install the plugin on USB or SD card . And send all your images to /media/nfr4xboot/NFR4XBootUpload/
then begin to install images.
After installing 9 images like this
Stop here and never make exit and choose options like this
After installing the first one change source image to install the second and so on.
After installing all images you can exit and it will be like that
In the other 3 internal images you only install the plugin and it reads the installed images by itself.
Enjoy.